Since November 1989, evidence of active filovirus infection has
been detected in cynomoigus (Macaca fascicularis) monkeys imported from
the Philippines to quarantine facilities in Virginia, Pennsylvania, and
Texas (1-3). CDC has used an indirect immunofluorescent antibody assay
(IFA) to examine approximately 2200 serum specimens from nonhuman
primates cynomoigus, rhesus, and African green monkeys) obtained from a
variety of settings (including the quarantine facilities in which
filovirus transmission has been documented). Approximately 10% of these
specimens have been positive for antibody to at least one of four
filovirus test antigens (Ebola-Zaire, Ebola-Sudan, Filovirus-Reston, and
Marburg).

Filovirus-related illness has not been observed in any human who
has been in contact with infected monkeys or their blood or tissues
since November 1989. However, antibody to one or more filovirus antigens
has been detected in six of the 178 persons tested as of April 23 (Table
1). Of the six persons, four-all animal handlers at one quarantine
facility-had serologic evidence of recent infection (4). it is likely
that one of the four was infected when he lacerated a finger while
performing a necropsy on an infected animal (4); the mode of
transmission for the other three is unknown. The other two persons were
seropositive at low titer and had evidence of past infection; one of
these persons, a worker at a facility that temporarily houses nonhuman
primates before delivery to U.S. quarantine facilities, has had regular
contact with quarantined monkeys for 3 years. The other person is
employed as an animal handler at a second quarantine facility.

Editorial Note: Epidemiologic and laboratory studies suggest that
there is a risk of transmission of filoviruses to humans that is
associated with routine handling and management of quarantined nonhuman
primates. Studies are in progress to quantify and better define the risk
for infection among persons working with nonhuman primates in U.S.
quarantine facilities and among their household and sexual contacts. In
addition, studies are under way to better define the frequency and
duration of importation of these agents into the United States.

Serious health consequences, including hemorrhagic disease and
death, have resulted from human filovirus infections in Europe (Marburg
virus) (5), and in Africa (Ebola and Marburg viruses) (6-9). To minimize
the health hazard from these agents and any potential hazard from the
newly recognized filovirus strains, on April 17, 1990, CDC implemented a
procedure (10), effective immediately, requiring the issuance of a
special permit from the Director, CDC, before importation of individual
shipments of cynomolgus, rhesus (M. mulatta ), and African green
(Cercopithecus aethiops) monkeys into the United States. Registered
importers of nonhuman primates have been notified of the requirement to
submit a detailed written plan that specifies steps that will be taken
to prevent exposure of persons and animals to filoviruses during the
entire importation and quarantine process for imported nonhuman
primates. This plan, together with a request for a special permit, must
be submitted to the CDC Director for consideration at least 30 days
before the proposed importation of any of the three nonhuman primate
species into the United States.